December 19-20 Talking Points - Part 3

[am19psu]

From the 18Z thread:

This is a point that I saw earlier and forgot to comment on here.

Early in season -> Ocean temps are still warm

Below normal land surface temps.

This sets up a very good natural baroclinic zone along the shoreline between these two contrasting temperatures for the storm to come up the coast.

Yep, I was just going to point out that post too, but for a different reason. The closer the track is to the coast, the more baroclinicity the storm will have to work with, and the deeper the potential intensity. That could be the other reason why the Euro is so much deeper.

[Chris L]

Convective feedback is such a nebulous thing to diagnose. The low was certainly warm core, but that's not uncommon for strong Nor'easters. I think I am still on the initialization bandwagon for the discrepancies. The s/w in the 12z Euro is so much stronger than any other s/w we've seen so far. If it were any other model, I would throw it out. As it is, I went for 4-8 for Philly Metro in my afternoon update for clients.

Your call sounds pretty good right now according to the ECM and trends. But I do have a question, though, are you taking banding in account? of course all this is moot if the ECM is going the wrong way tonight.

[tmagan]

From the 18Z thread:

This is a point that I saw earlier and forgot to comment on here.

Early in season -> Ocean temps are still warm

Below normal land surface temps.

This sets up a very good natural baroclinic zone along the shoreline between these two contrasting temperatures for the storm to come up the coast.

While true, it is the upper-level pattern that dictates the surface features, otherwise every winter storm would just come up the east coast.

[am19psu]

Your call sounds pretty good right now according to the ECM and trends. But I do have a question, though, are you taking banding in account? of course all this is moot if the ECM is going the wrong way tonight.

No. I'm a national forecaster, so for mesoscale events like banding, I just cover it with "locally higher amounts."

[_AR_]

While true, it is the upper-level pattern that dictates the surface features, otherwise every winter storm would just come up the east coast.

Yes, but it helps tremendously. Upper levels are supportive of the track. There is nothing major kicking this out to sea.

[dtk]

I don't either--I was a little unsure on that reasoning too. It's definitely interesting how wide the spread is. Usually at this range, with the Euro and it ensembles showing hits at 72-84 hrs...there would be some decent confidence. But the fact is that there isn't--and with good reason, too.

It was encouraging to see the SREFs come so far north and west and I'm hoping we see the same idea at 21z. A few SREF members were actually very far west---more than the Euro.

This storm is becoming the poster child for why / how ensemble systems are so useful.

[phlwx]

I don't see that as convective feedback, so much as a very wound up system with a bent-back warm front and warm seclusion...a common feature of many strong extratropical storms. Still I question whether the storm will wind up quite that much--all the players would have to come together just right.

This. I worry that the phase is too "perfect" on the Euro.

[jm1220]

This. I worry that the phase is too "perfect" on the Euro.

The Euro as it stands now is probably the most "perfect" this storm can be given how weak the upper air features are. It makes sense that the storm will go kaboom at the coast or just offshore due to the large temp. contrasts we have now, which could argue for the further west Euro/GGEM, but also that if there's no energy, there can't be a storm-so the presence of that shortwave is absolutely crucial.

[wkd]

This storm is becoming the poster child for why / how ensemble systems are so useful.

Hope to see you posting here more. I learned a lot from your input and the back and forth you had with ALEX.

[bluewave]

I don't see that as convective feedback, so much as a very wound up system with a bent-back warm front and warm seclusion...a common feature of many strong extratropical storms. Still I question whether the storm will wind up quite that much--all the players would have to come together just right.

That sounds right.If things aren't going to line up perfectly like the 12z Euro, then I suspect we''ll see an eastward Euro shift as early as tonight.

[ace0927]

This storm is becoming the poster child for why / how ensemble systems are so useful.

i might be crazy but the 18Z GFS individual members dont look very promising. Maybe 1 or 2 scrap us, the rest are a miss....

[Edge Weather]

The 18z GFS as a whole did not look very promising. I believe the 0z GFS will be a different story. I say this because we have seen time after time how the GFS follows behind the ECMWF one or two runs. I would be in absolute shock if the GFS and NAM do not look much more favorable this evening.

i might be crazy but the 18Z GFS individual members dont look very promising. Maybe 1 or 2 scrap us, the rest are a miss....

[SnowGoose69]

The 18z GFS as a whole did not look very promising. I believe the 0z GFS will be a different story. I say this because we have seen time after time how the GFS follows behind the ECMWF one or two runs. I would be in absolute shock if the GFS and NAM do not look much more favorable this evening.

If the GFS and NAM ultimately lead the way back to this being a non-event with the Euro following we can basically say all models at one point or another were terrible with this storm.

[joey]

If the GFS and NAM ultimately lead the way back to this being a non-event with the Euro following we can basically say all models at one point or another were terrible with this storm.

Exactly. The key question then- do we learn from it? Highly unlikely.

[am19psu]

If the GFS and NAM ultimately lead the way back to this being a non-event with the Euro following we can basically say all models at one point or another were terrible with this storm.

I'd argue we can already say that.

[RutgersWx92]

The 18z GFS as a whole did not look very promising. I believe the 0z GFS will be a different story. I say this because we have seen time after time how the GFS follows behind the ECMWF one or two runs. I would be in absolute shock if the GFS and NAM do not look much more favorable this evening.

It would indeed be very shocking to see the ECMWF bust so terribly within what is normally it's pretty accurate range. A widespread I-95 MECS depicted just 72 hours out on the Euro (with its ensembles in general agreement) turning into a non-event? Has that ever even happened before? Not saying that definitely won't happen, but it would be quite shocking.

[Chris L]

If the GFS and NAM ultimately lead the way back to this being a non-event with the Euro following we can basically say all models at one point or another were terrible with this storm.

I agree with this because of the upper air pattern has been a very tough setup to predict largely due to the blocking in Northern Canada and the timing of the Polar Vortex splitting. This is not your classic snow event by any means, which would certainly been handled by the models significantly better had we just had: Block, 50-50 Low, Miller A Gulf Low, surging into a cold dome. This requires quite remarkable timing and the depth of speed to work. That is why the models are struggling and will struggle.

[bluewave]

Sometimes I miss the good old days like January 20,1978 when there was no worrying ahead of time and we wound up with a surprise snowstorm.

[blazess556]

21z srefs rolling

[jdt]

It would indeed be very shocking to see the ECMWF bust so terribly within what is normally it's pretty accurate range. A widespread I-95 MECS depicted just 72 hours out on the Euro (with its ensembles in general agreement) turning into a non-event? Has that ever even happened before? Not saying that definitely won't happen, but it would be quite shocking.

It could shift back east 100 miles and thus from a sensible weather stand point be a non-event for many or most but meteorlogicaly the storm still blows up into a beast just 100 miles further east. I would not consider that a terribly bust 72 hours out. Maybe not the precise accuracy would hope for but far from a bust imo. I do think the 12z Euro showed the absolute best possible outcome. Cannot get any better on the 0z so it either is nearly identical or less severe in some regard.

[Colin]

srefs notably flatter through 42 compared to 15z

[Neblizzard]

I agree with this because of the upper air pattern has been a very tough setup to predict largely due to the blocking in Northern Canada and the timing of the Polar Vortex splitting. This is not your classic snow event by any means, which would certainly been handled by the models significantly better had we just had: Block, 50-50 Low, Miller A Gulf Low, surging into a cold dome. This requires quite remarkable timing and the depth of speed to work. That is why the models are struggling and will struggle.

Respectfully disagree, we have a west based -NAO, displaced polar vortex, and a weak 50/50 low. The only player that we don't have on the field and is typical in many KU snowstorms is the +PNA. Also notice there is somewhat of a STJ connection over the southwest. It's always about timing and if this storm phases and bombs, it's because of the factors I stated above....

[joey]

srefs notably flatter through 42 compared to 15z

yep- scrapes eastern MA.

[Colin]

srefs further east

[redbanknjandbigbasslakepa]

way further east. that 12z euro run was on crack for sure.

[blazess556]

21z SREF used 18z data. watch the nam which has 00z data

[chubbs]

I agree with this because of the upper air pattern has been a very tough setup to predict largely due to the blocking in Northern Canada and the timing of the Polar Vortex splitting. This is not your classic snow event by any means, which would certainly been handled by the models significantly better had we just had: Block, 50-50 Low, Miller A Gulf Low, surging into a cold dome. This requires quite remarkable timing and the depth of speed to work. That is why the models are struggling and will struggle.

Another factor is the interaction of relatively weak short waves to trigger storm formation. Not like the strong features we had last year.

[Edge Weather]

If that is the case, then the SREF's are completely pointless.

21z SREF used 18z data. watch the nam which has 00z data

[blazess556]

00z NAM stronger with southern shortwave and 4 corners shortwave

[mitchnick]

If that is the case, then the SREF's are completely pointless.

they would have more recent surface data, so who knows